Chemical signals generated at synapses are highly limited in both spatial range and time course, so that experiments studying such signals must measure and manipulate them in both these dimensions. We describe an optical system that combines confocal laser scanning microscopy, to measure such signals, with focal photolysis of caged compounds. This system can elevate neurotransmitter and second messenger levels in femtoliter volumes of single dendrites within a millisecond. The method is readily… CONTINUE READING